Abstract

An isobaric-isothermal Gibbs ensemble Monte Carlo simulation has been carried out to study the adsorption of a model surfactant/solvent mixture in slit nanopores. The adsorption isotherms, the density distributions, and the configuration snapshots were simulated to illustrate the adsorption and self-assembly behaviors of the surfactant in the confined pores. The adsorption isotherms are stepwise: a two-step curve for the smaller pore and a three-step one for the larger pore. The adsorption isotherms and the interfacial aggregatestructure of the surfactants in the pores with various sizes show a qualitatively consistent performance with the previous experimental observation. The micelle size distributions of the adsorbed surfactantaggregates have been analyzed in order to understand the adsorption mechanism, which suggests that the step rise in the surfactantadsorption is associated with the considerable formation of the micelleaggregates in the confined pores. The effect of the interaction between the pore surface and the surfactant on the adsorption behavior has also been investigated. The simulation results indicate that a change in the interaction can modify the shape of adsorption isotherms. A nonlinear mathematical model was used to represent the multistep adsorption isotherms. A good agreement between the model fitting and the simulation data was obtained for both the amount of adsorption and the jump point concentration.